Apparatus, method and reusable model-structure for impact testing vehicle components

ABSTRACT

The front body assembly of a vehicle is simulated by a reusable model-structure (6) featuring a pair of side members (8, 9) collapsible accordion fashion and each comprising a number of arms (16, 18) hinged in series with one another by respective articulating means (19, 20), and a number of hydraulic friction joints (20) constituting at least some of the articulating means. Each hydraulic joint (20) presents an adjustable sliding torque by virtue of being connected to pressurized fluid supply means (43) via a respective pressure regulating valve (42). Once calibrated, the model-structure (6), which thus presents the same collapse performance as the front body assembly being simulated, is fitted with the test component (2) and used for impact testing; and, following impact, the collapsed model-structure (6) is restored to its original configuration by means of hydraulic actuators (38), after first zeroing the pressure of the hydraulic joints (20).

TECHNICAL FIELD

The present invention relates to an apparatus for impact testing themechanical performance of vehicle components, in particular the frontload-bearing components of a vehicle body or structure, such as thefront cross member, engine supporting frame and similar, but withoutinvolving total destruction of the vehicle.

The present invention also relates to a test method employing the aboveapparatus, and to a reusable, collapsible model-structure forming themain part of the apparatus, designed to receive the test component, andwhich, with the component on board, provides for standard impact testingby accurately simulating the dynamic performance of any existing frontvehicle body assembly.

BACKGROUND ART

Before launching a new model on to the market, or whenever improvementsor changes are made to the load-bearing components of existing models,all car manufacturers conduct "live" impact tests to determine themechanical response of vehicle body and internal passenger compartmentcomponents to dynamic design stress. At present, these tests involve agood deal of expense in that simply determining the response of onecomponent (e.g. the engine supporting frame, front cross member, bumper,seat guide, safety belt fasteners, etc.) involves the total destructionof vehicles identical to those for marketing. For, even though thedeformation performance of the overall vehicle structure may bedetermined easily and cheaply by means of full-vehicle impact testsconducted for other purposes (e.g. passenger safety tests using amanikin), this is not sufficient for extrapolating the performance ofindividual components.

DISCLOSURE OF INVENTION

It is an object of the present invention to provide an apparatus for"live" impact testing vehicle components, particularly single frontvehicle body components, without requiring total destruction of thevehicle.

In particular, it is an object of the present invention to provide amechanical "model" structure for simulating, without damage, the impactperformance of any front vehicle assembly, so as it may be reused innumerous tests, in order to be used in conjunction with the aboveapparatus for determining the resistance of vehicle body and internalpassenger compartment components, providing for drastically reducing thecost of current test methods.

Finally, it is a further object of the present invention to provide atest method employing the above apparatus and wherein the abovemodel-structure is used in lieu of the complete vehicle.

According to the present invention, there is provided an apparatus forimpact testing vehicle components, characterized by the fact that itcomprises a reusable trestle type model-structure designed, on impact,to switch from an extended to a collapsed configuration with the samedynamic performance as the front vehicle body assembly being simulated,the model-structure comprising a number of substantially rigid,load-bearing elements articulated by means of friction elements with anadjustable sliding torque; the apparatus also comprising means forsupporting the model-structure; means for selectively calibrating thesliding torque of each friction element to a predetermined value abovewhich the friction element permits relative rotation of the load-bearingelements connected by it, and hence collapse of the model-structure; andat least one actuator for restoring the model-structure, after impact,from the collapsed configuration to the same extended configurationprior to impact; the model-structure being designed, at least in theextended configuration, to receive at least one vehicle test component.

As opposed to using, and hence destroying, a high-cost productionvehicle, the test apparatus according to the present invention thusprovides for employing a low-cost model-structure which is in no waydamaged during testing and may thus be reused for any number of tests.

The above apparatus is employed in a vehicle component impact testmethod, characterized by the fact that it comprises the followingstages:

setting up a reusable model-structure for simulating the dynamiccollapse performance of the vehicle of which the test component formspart; the model-structure being formed by connecting a number ofsubstantially rigid, load-bearing elements in articulated manner bymeans of friction elements with an adjustable sliding torque;

so calibrating said model-structure as to enable it, upon impact, toswitch from an extended to a collapsed configuration with the samedynamic performance as the front vehicle body assembly being simulated;said calibrating stage being performed by trial and error, by subjectingthe model-structure to a predetermined amount of dynamic stress,determining the dynamic collapse performance of the structure, restoringthe structure to the extended configuration, and separately adjustingthe sliding torque of each friction element until the dynamic collapseperformance of the model-structure corresponds with the knownperformance of the body assembly being simulated;

fitting the test component to the extended model-structure, andconducting a normal impact test using the model-structure in lieu of thevehicle to which the test component is to be mounted.

The known deformation performance of each vehicle as a whole is thusused for accordingly calibrating a single model-structure which, oncecalibrated, provides for accurately simulating the deformationperformance of the front assembly of a given vehicle model. As such, onemodel-structure and one test apparatus according to the presentinvention provide for all-round testing of substantially any existingvehicle model.

In particular, a reusable model-structure is employed, characterized bythe fact that it comprises a first and second trestle type side membercollapsible accordion fashion, located parallel/to each other, and eachcomprising a number of arms hinged in series with one another byrespective articulating means, and a number of hydraulic friction jointsconstituting at least some of the articulating means.

BRIEF DESCRIPTION OF THE DRAWINGS

A non-limiting embodiment of the present invention will be described byway of example with reference to the accompanying drawings, in which:

FIGS. 1 and 2 respectively show an elevation and top plan view of a testapparatus in accordance with the present invention;

FIGS. 3 and 4 respectively show an enlarged rear view of the front, andan enlarged, partially sectioned detail, of a model-structure employedon the FIG. 1 and 2 apparatus;

FIGS. 5 and 6 respectively show an elevation and top plan view of theFIG. 3 and 4 model-structure in use.

BEST MODE FOR CARRYING OUT THE INVENTION

With reference to FIGS. 1, 2 and 5, 6, number 1 indicates an apparatusfor destructive impact testing vehicle components--in the non-limitingexample shown, the front frame 2 supporting the engine 3 of a vehicle 4(FIGS. 5, 6) of which the dynamic deformation performance of at leastthe front body assembly 5 is known.

According to the main characteristic of the present invention, apparatus1 comprises a twin-trestle type model-structure 6, designed to receivetest component 2 and to simulate, during normal impact testing, theknown dynamic collapse performance of front body assembly 5 of vehicle4. As such, known impact testing for determining the on-vehiclemechanical performance of component 2, and consisting in driving vehicle4 as a whole, complete with component 2, at a given speed against afixed obstacle, may be performed using, in lieu of vehicle 4,model-structure 6 which provides in every way for mechanicallysimulating front body assembly 5.

According to the present invention, model-structure 6 is formed, on theone hand, so as to undergo no damage during impact testing, thusenabling it to be reused, as will be seen, for any number of tests; and,on the other hand, so as to selectively simulate the performance of thefront body assembly of vehicles 4 of different types and models, bysimply "setting up" or calibrating model-structure 6 on apparatus 1prior to testing.

With reference also to FIGS. 3 and 4, model-structure or mechanicalsimulator 6 according to the present invention comprises two sidemembers 8, 9 in the form of three-dimensional trestle structurescollapsible lengthwise in accordion fashion (i.e. in the direction ofrespective axes A and B--FIG. 6); and two rigid, respectively front andrear cross members 10, 11 defined by load-bearing base elements in theform of a plate. Cross members 10, 11 are useful for achieving unity ofmodel-structure 6 even when detached from apparatus 1, and forprotecting side members 8, 9 during impact, but are not strictlyindispensable as regards operation of structure 6.

More specifically, side members 8, 9 and cross members 10, 11 arearranged parallel to each other so that, viewed from above, structure 6presents the form of a quadrilateral; and are connected to one anotherat the corners of quadrilateral structure 6 by hinge type articulatingmeans defined, for cross member 10, by a pair of idle vertical-axis pins12, and, for cross member 11, by a pair of known hydraulic frictionjoints 13 with a rotation axis parallel to that of pins 12, so that,viewed from above, model-structure 6 defines an articulatedquadrilateral.

Each identical side member 8, 9 comprises a number of substantiallyrigid, load-bearing elements defined by pairs of parallel arms 16, 18hinged in series and in zig-zag fashion to one another by respectivearticulating means, the axes of rotation of which are all parallel toone another, and perpendicular to axes A, B and to the rotation axes ofpins 12 and friction joints 13. According to the present invention, saidarticulating means consist alternately of respective idle pins 19, and anumber of hydraulic friction joints 20 of the same type as joints 13 buta different model.

To support joints 20 and ensure the structural solidity of side members8, 9, these also comprise a number of rigid rectangular frames 21, e.g.made of bent, welded tubular metal elements, increasing in size fromcross member 10 towards cross member 11 (FIGS. 3 and 6), and therespective top and bottom horizontal portions 22 of which are fittedintegral with hydraulic friction joints 20, e.g. by means of brackets 23either welded or locked by further joints 25, so that, on either side ofeach frame 21, two pairs of arms 18 (one from bottom horizontal portion22, and one from top portion 22) extend towards cross member 11, and twopairs of arms 16 towards cross member 10. Further end pairs of arms 16and 18 provide for connecting side members 8, 9 in articulated manner tocross members 10, 11 by means of pins 26 parallel to pins 19, and viapins 12 and friction joints 13 described previously.

As shown particularly in FIG. 4, known hydraulic friction joints20--e.g. of the type known as SAFESET marketed by MONDIAL ofMilan--present an adjustable sliding torque below which any relativemovement of connected arms 16, 18 is prevented, and above which arms 16are permitted to rotate, with a predetermined amount of friction, inrelation to arms 18 and about mutual hinge axes D (FIGS. 3 and 4)parallel to the axes of pins 19.

In the example shown, each joint 20 comprises a pin 30 housed idlyinside a fluidtight housing 31 integral with respective frame 21. Arms16, 18 are fitted angularly integral with pin 30, and cooperatelaterally, on either side, with respective friction disks 32 fittedinside and integral with housing 31 and therefore angularly fixed butaxially slidable in relation to pin 30. Friction disks 32 and arms 16,18 are acted on by a piston 33 activated by the hydraulic pressureinside a chamber 34 formed inside housing 31 and connected by a pipe 35to a pressurized fluid, e.g. oil, source. Friction disks 32 thus exerton arms 16, 18 a retaining torque proportional to the hydraulic pressureinside chamber 34 and, hence, to the axial pressure exerted by piston33; and said sliding torque of the joint is that which, applied to pins30 by arms 16, 18, exceeds the retaining torque exerted by frictiondisks 32 by just enough to slide friction disks 32 and hence rotate arms16, 18 in relation to housing 31.

Structure 6 therefore behaves as a statically determined structure aslong as the stress applied to it (e.g. by cross member 10) is such thatthe torques transmitted to arms 16, 18 are below the sliding torque ofeach joint; whereas it becomes a reticulated structure with at least afew weak nodes when said stress is such that the torque transmitted toeven only one arm 16 or 18 is greater than the retaining torque exertedby friction disks 32, i.e. greater than the sliding torque of therespective joint 20. As the latter torque is proportional to thehydraulic pressure in respective chamber 34, by appropriately regulatingthis pressure differently from one joint to another, it is possible toachieve different responses of the same structure 6 to the same systemof external mechanical stress applied to it.

The same also applies to joints 13 (not shown in detail) only in thiscase relative to axes perpendicular to axes D and parallel to pins 12.Consequently, when a side member 8, 9 as a whole transmits to respectivejoint 13 a torque greater than the sliding torque of the joint, thequadrilateral defined by side members 8, 9 and cross members 10, 11becomes statically weak, thus enabling rotation about the axes of pins12 and joints 13. As such, model-structure 6 may selectively assume twoconfigurations: an extended configuration (FIGS. 1, 2 and 5, 6) whereinarms 16, 18 are arranged at an angle to each other, the size ofstructure 6 as a whole is comparable with that of the front bodyassembly being simulated (FIGS. 5, 6), and structure 6 may be fittedwith at least one vehicle test component (in this case, frame 2); and acollapsed configuration (not shown) wherein structure 6 is compressedaccordion fashion along axes A, B, and possibly also positionedobliquely in relation to axes A, B by virtue of also rotating aboutjoints 13 and pins 12.

For restoring it from the collapsed to the extended position, structure6 as shown comprises a number of hydraulic actuators 38 mounted, in theexample shown, between each top and bottom/pair of arms 16, 18 of eachjoint 20, at connecting pins 19, and which, when withdrawn/extended,provide for moving in relation to each other the arms 16, 18 connectedto the opposite ends of each actuator.

It should be stressed that model-structure 6 as described above ispurely indicative, and may differ widely in design with no effect onperformance. For example, according to variations not shown, actuators38 may be replaced by a single actuator connected to the opposite endsof cross members 10 and 11, or by one or more actuators forming part ofapparatus 1; four-armed friction joints 20 may be replaced by twice asmany hydraulic friction joints, each having one arm 16 and one arm 18arranged side by side in pairs on each portion 22 of frame 21; forachieving even greater articulation of structure 6, joints 25 ofbrackets 23 may also be in the form of hydraulic friction joints (FIG.4) similar to joints 20, thus enabling pairs of arms 16, 18 in each setto rotate about an axis E (FIG. 3) perpendicular to respective rotationaxis D of respective joint 20.

For better exploiting model-structure 6, apparatus 1 also comprisesmeans for supporting structure 6 and defined, in the example shown, by aframe type slide 40 (FIGS. 1 and 2) mounted in fixed manner (orpermitted to slide by releasing appropriate lock means) on a supportingbed 41; means for selectively calibrating the sliding torque of eachfriction disk 32 of joints 20 and 13; and, if not provided onmodel-structure 6, at least one actuator for restoring structure 6,after impact, from the collapsed configuration to the same extendedconfiguration prior to impact.

In particular, said calibrating means comprise respective known valves42 for regulating the hydraulic supply pressure of each hydraulicfriction joint 13, 20 between a minimum zero value and a maximum valueequal, for example, to the head of a pump 43 supplying pressurized oilfor activating friction joints 13, 20; means, consisting for example ofknown coiled tubes (not shown), for supplying said pressurized oilproduced by pump 43 to hydraulic friction joints 13, 20 via valves 42,and so enabling hydraulic connection while at the same time permittingrelative movement of the various components of structure 6; a thrustdevice 46 for "hammering", and so exerting predetermined dynamic stresson, structure 6; and means for displaying a quantity proportional to thesliding torque of each joint 13, 20--in the example shown, a set ofgauges 47 showing the supply pressure of each friction joint 13, 20, andmounted together with valves 42 on a console 48 fixed to bed 41.

In the example shown, device 46 is fitted integral with bed 41 (possiblyin removable manner), and consists of a hammer or ram 49 powered by aknown, e.g. hydraulic, actuating device 50 by which model-structure 6,fixed to bed 41 by supporting slide 40, is subjected via hammer or ram49 to dynamic stress similar to that produced by impact of structure 6at a predetermined speed against a fixed obstacle.

According to the present invention, apparatus 1 and structure 6 areemployed in a method for destructive impact testing vehicle componentssuch as frame 2 by simulating real on-vehicle impact conditions of thetest component. The first stage in the method consists in fixingreusable model-structure 6 in the extended position to bed 41, afterwhich joints 13, 20 of structure 6 are calibrated using device 46, alsofixed to bed 41, as shown in FIGS. 1 and 2. More specifically, thecalibrating stage consists in so setting valves 42 as to supply frictionjoints 13, 20 with oil at predetermined pressures as required; structure6 is then subjected, by hammer or ram 49 striking cross member 10, tosufficient impact to collapse it, while at the same time determining,using known, e.g. optical and/or electromechanical means (not shown),the dynamic collapse performance of structure 6 as a result of impact;and, finally, structure 6 is restored to the original extendedconfiguration by adjusting friction disks 32 so that each presents asliding torque of zero (i.e. the supply pressure of joints 13, 20 iszeroed by fully closing valves 42 or a main valve for cutting off supplyby pump 43) and by immediately operating actuators 38.

At this point, the above operations are repeated in trial-and-errorfashion, each time adjusting the supply pressure of each joint 13, 20 bymeans of respective valve 42, until the passage of structure 6 from theextended to the collapsed configuration as a result of the blowinflicted by hammer 49 is identical to the known performance of frontbody assembly 5 being simulated. When this is achieved, structure 6 isready for use, after first assembling the test component.

The actual impact test may be performed on apparatus 1 using hammer 49,or in conventional manner by driving structure 6 against a fixedobstacle. For example, structure 6, still connected by extendible hosesto valves 42 and pump 43 for pressurizing joints 13, 20, is removed fromfixed slide 40 and mounted on an identical slide (not shown) movablealong bed 41 or a similar bed of a conventional test station to the sideof apparatus 1; the slide with structure 6 fitted with the testcomponent is driven at predetermined speed against a known fixed stop(not shown) so as to collapse structure 6; the test component isrecovered and examined; and, according to the present invention,structure 6 is restored to the original extended configuration (byzeroing the supply pressure of joints 13, 20 and operating actuators 38)ready for testing another similar or different component.

According to one characteristic of the above test method, joints 13, 20are so designed that the maximum sliding torque of friction disks 32 isalways less than the minimum value which, during impact testing or eventhe calibrating stage, would stress the load-bearing elements 10, 11,16, 18, 21 of structure 6 over and above their yield point, thuspreventing any possibility of damage to model-structure 6 during impacttesting, and so enabling it to be reused any number of times. Moreover,by simply repeating the calibrating stage, the same model-structure 6may be used for simulating the performance of different vehicle bodystructures 5, thus further enhancing the versatility and reducing thecost of the method according to the present invention.

I claim:
 1. An apparatus (1) for impact testing vehicle components (2),characterized by the fact that it comprises a reusable trestle typemodel-structure (6) designed, on impact, to switch from an extended to acollapsed configuration thereby simulating the dynamic performance of afront vehicle body assembly to be tested, said model-structure (6)comprising a number of substantially rigid, load-bearing elements (16,18) articulated by means of friction elements (20) with an adjustablesliding torque; said apparatus (1) also comprising means (40) forsupporting said model-structure (6); means (42) for selectivelycalibrating the sliding torque of each of said friction elements. (20)to a predetermined value above which said friction elements permitsrelative rotation of said load-bearing elements (16, 18) connected byit, and hence collapse of said model-structure (6); and at least oneactuator (38) for restoring said model-structure (6), after impact, fromthe collapsed configuration to the same extended configuration prior tothat of impact; said model-structure (6) being designed, at least in theextended configuration, to receive at least one of said vehicle testcomponents (2).
 2. An apparatus (1) as claimed in claim 1, characterizedby the fact that said friction elements are hydraulic friction elements(20); and by the fact that said calibrating means comprise respectivevalves (42) for regulating a hydraulic supply pressure operativelyassociated with each of said hydraulic friction elements (20) of saidmodel-structure between a minimum zero value and a maximum value; andmeans (43) for supplying said hydraulic friction elements (20) withpressurized fluid via said valves.
 3. An apparatus (1) as claimed inclaim 1 characterized by the fact that said calibrating means comprise athrust device (46) for subjecting said model-structure (6), fixed tosaid supporting means (40), to predetermined dynamic stress of the typeresulting from impact; and means (47) for displaying a quantityproportional to the sliding torque of each said friction element (20).4. A method of impact testing vehicle components (2), characterized bythe fact that it comprises the following stages:a) setting up a reusablemodel-structure (6) for simulating the dynamic collapse performance ofthe vehicle of which the test component forms part; the model-structure(6) being formed by connecting a number of substantially rigid,load-bearing elements (10, 11; 16, 18) in articulated manner by means offriction elements (13, 20) with an adjustable sliding torque; b) socalibrating said model-structure (6) as to enable it, upon impact, toswitch from an extended to a collapsed configuration thereby simulatingthe dynamic performance of a front vehicle body assembly to be tested;said calibrating stage being performed by trial and error, by subjectingsaid model-structure (6) to a predetermined amount of dynamic stress,determining the dynamic collapse performance of said structure (6),restoring said structure to the extended configuration, and separatelyadjusting the sliding torque of each friction element (13, 20) until thedynamic collapse performance of said model-structure corresponds with aknown pre-determined performance of the body assembly being simulated;c) fitting said test component (2) to said extended model-structure (6),and conducting a normal impact test using said model-structure in lieuof a vehicle to which said test component (2) is to be mounted.
 5. Amethod as claimed in claim 4, characterized by the fact that, followingimpact testing, said model-structure (6) is restored to the extendedconfiguration for further testing.
 6. A method as claimed in claim 5,characterized by the fact that the extended configuration is restored byso adjusting said friction elements (13, 20) whereby each presents azero sliding torque, and by acting on at least two opposite saidload-bearing elements (10, 11; 16, 18) by means of an actuator (38) soas to produce a relative movement of said two load-bearing elements. 7.A method as claimed in claim 5 characterized by the fact that saidfriction elements (13, 20) are so adjusted as to present a maximumsliding torque below the value which, during impact testing, wouldstress the load-bearing elements (10, 11; 16, 18) over and above theiryield point.
 8. A reusable model-structure (6) for simulating, duringimpact testing, the dynamic collapse performance of a vehicle front bodyassembly; characterized by the fact that it comprises first (8) andsecond (9) trestle type side members collapsible in an accordionfashion, located parallel to each other, and each comprising a number ofarms (16, 18) hinged in series with one another by respectivearticulating means (19, 20), and a number of hydraulic friction (20)joints constituting at least some of said articulating means.
 9. Amodel-structure (6) as claimed in claim 8, characterized by the factthat each said hydraulic joint (20) is connected by a respectivepressure regulating valve (42) to pressurized fluid supply means (43),so that each presents an adjustable sliding torque below which anyrelative movement of said connected arms (16, 18) is prevented, andabove which said arms (16, 18) are permitted to rotate in relation toone another with a predetermined amount of friction and about theirrespective mutual hinge axes.